sedimentary

Conglomerate

Conglomerate (clastic sedimentary rock)

AI-generated identification · may be incorrect

Hardness: Variable (consists of diverse rounded clasts in a fine-grained matrix); Color: Multicolored (browns, grays, reds); Luster: Dull to earthy; Structure: Clastic with rounded grains larger than 2mm; Specific Gravity: 2.6-2.9.

Color: Multicolored (browns, grays, reds)
Luster: Dull to earthy

Identified March 18, 2026More sedimentary →

Explore Conglomerate in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed in high-energy environments like riverbeds, alluvial fans, or beaches where water current is strong enough to transport large, rounded pebbles. Over time, these sediments are buried and lithified by a matrix of sand, silt, or chemical cement (calcite or silica).

Uses & applications

Primarily used as aggregate in the construction industry for roads and buildings. Occasionally used in architecture as decorative facing stone or as a source of the minerals contained within the pebbles (e.g., gold or diamonds found in ancient conglomerate beds).

Geological facts

Conglomerate is often nicknamed 'puddingstone' because the rounded pebbles look like raisins in a pudding. Identifying the composition of the pebbles can tell geologists exactly where the ancient river or glacier originated from millions of years ago.

Field identification & locations

Identify in the field by looking for rounded, water-worn pebbles larger than 2mm cemented together. It is commonly found in ancient riverbeds or mountain basins. For collectors, look for 'polygenic' samples with many different colorful rock types in one piece.